Spray guns are utilised in many applications in order to quickly and accurately apply paint, lacquer or bonding substances etc. to a surface. In many such applications, the quantity of paint or other substance applied to the surface, and hence the film thickness of the resulting coating must be extremely accurate. Examples of such applications include e.g. the automotive and aerospace industries.
An example of a known spray gun is described in Irish Patent Publication No. 120249 which describes a spray gun having a reciprocating trigger which, when pressed by a user, translates a paint release needle into an open position in order to release paint from the gun in a controlled fashion. The reciprocating trigger also simultaneously actuates an air valve in order to release a first flow of air which ejects paint from the apparatus as a jet, and a second (“horns”) flow of air which is imparted tangentially on the jet of paint as it leaves the apparatus in order to shape the jet of paint into a fan shape.
One problem with such known spray guns is that, over a short period of time, wear and tear of the reciprocal trigger mechanism can cause misalignment between the trigger, air valve and paint release assembly. Such misalignment causes inaccuracies in the quantity of paint sprayed for a given displacement of the trigger and hence causes inaccuracies in the film thickness of paint applied. Furthermore, the trigger in such spray guns has a tendency to become jammed (especially in the “on” position) due to mechanical play arising in the interaction between the components of the trigger and the paint release assembly against the spray gun's main body.